Neil wrote about Blake's change in character:
I think the character shift actually begins in TWB itself. His repeated 'No drugs' to Havant, his refusal to offer any defence at his trial - these are the first stirrings of the confident, assertive Blake who sets out to take the London in the next episode. Not necessarily a change of character at all, since at the start of TWB he is totally out of his depth as to what's going on, and just coming off the suppressants
What impressed me most when I saw the episode in full (I missed the first broadcast, and for a long time had seen it only hacked to bits on the compilation tape) was the way Gareth conveyed the shift in his face. At the start of the episode, Blake's face is smooth, bland and youthful. He doesn't actually look like the Blake I know from the rest of the series until we see him in his cell, and then talking to Havant. How much of his memory has returned I don't know, but he's beginning to regain his dissident mindset. He looks older, stressed, but at the same time more vital.